A gray scale image cleaning algorithm for improved check code line OCR. An image processing system for processing a gray scale image is provided that includes: a system for generating a first thresholded black white image from the gray scale image; a system for generating a second thresholded black white image from the gray scale image, wherein the second thresholded black white image is generated with a higher threshold value than the first thresholded black white image; and a system for logically combining the first and second thresholded black white images to generate a composite image.